#define _CRT_SECURE_NO_WARNINGS 1

class Solution {
public:
    bool lemonadeChange(vector<int>& bills) {
        int five = 0, ten = 0;
        for (int i = 0; i < bills.size(); i++)
        {
            if (bills[i] == 5)
                five++;
            if (bills[i] == 10)
            {
                if (five)
                {
                    five--;
                    ten++;
                }
                else
                {
                    return false;
                }
            }
            if (bills[i] == 20)
            {
                if (five && ten)
                {
                    five--;
                    ten--;
                }
                else if (five >= 3)
                {
                    five -= 3;
                }
                else
                {
                    return false;
                }
            }
        }
        return true;
    }
};